Vacuum Leak?

2001 FORD EXPEDITION
150,000 MILES • 4.6L • V8 • 2WD • AUTOMATIC
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DFOSTER90
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I keep getting a DTC for a small vacuum leak, but the truck seems to be running fine. Only place I have found a leak was in the A/C vacuum line that goes to the vacuum reservoir, and I repaired that. Is there any other common area where there is a vacuum leak or do you have a diagram of the vacuum lines? Thanks
Jul 25, 2025 at 7:29 AM
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STRAILER
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Yes these engines had a problem with the PCV hose, you need to remove it to inspect. The hose falls apart internally. Here is a video to help find the leak as well, the machine is $65.00 on Amazon.

https://amzn.to/4f8Jqt4

and the video:

https://www.youtube.com/watch?v=LRKWV4Are5c&t

Check out the images (below). Let us know how it goes.
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Jul 25, 2025 at 12:39 PM
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DFOSTER90
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Okay. I will take a look at it. The DTC is P0442 by the way and this is what the scanner reads.
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Jul 25, 2025 at 1:11 PM
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STRAILER
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Okay, this is not an engine vacuum leak.

DTC P0442 - Evaporative Emission Control System Leak Detected (Small Leak)

So, I would check the gas cap O ring, this is a common place to leak. Next, check the EVAP lines from the engine to the fuel tank, and finally if you can find the leak use a smoke machine here is a video to help show you, I have seen the charcoal canister crack and give this code.

https://www.youtube.com/watch?v=LRKWV4Are5c&t

You can get one for about $65.00 from Amazon.

https://amzn.to/4l1c2px

Let us know how it goes.
Jul 25, 2025 at 1:25 PM
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DFOSTER90
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Okay thanks! I'll give that a try and see what happens.
Jul 25, 2025 at 2:01 PM
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STRAILER
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Please do the vacuum leak machine works well.
Jul 27, 2025 at 10:36 AM